The field of application of the invention relates to the identification of an aircraft's flight mechanics, that is to say the comparison of the actual movements of an aircraft with their modeling as well as, if appropriate, the adjustment of parameters of the model used to achieve optimal fidelity of this model.
Hence, a trials protocol is implemented which indicates, generally, a way to carry out in-flight trials for a determined purpose. To this end, a series of predefined sequences of airfoil deflections is defined in a standard manner. In the case of flight mechanics, the protocols consist, in a standard manner, of in-flight trials solely carried out in open loop on the aircraft, that is to say no aircraft attitude control system is engaged in the course of these trials. In the particular case where the aircraft is naturally unstable, a control system which is limited to a minimum stabilizer is simply envisaged. The protocols are carried out in the form of trials campaigns. In the course of these trials, predefined control sequences are applied to the aircraft. The controls applied, as well as the resulting outputs, are measured on the aircraft and are recorded. They are processed a posteriori. The actual controls measured on the aircraft in the course of the in-flight trials are rerun on a simulation model. The actual outputs measured on the aircraft are thereafter compared with the outputs from the simulation model. A registration of certain effects can then be performed. The quality (accuracy, etc.) of the identification (of the flight mechanics) depends on the quality (accuracy, etc.) of each of the aforesaid steps. It will be noted that the present invention pertains essentially to improving the first step, namely the trials protocol.
As indicated previously, the fundamental characteristic of a standard trials protocol resides in the fact that it is composed of in-flight trials carried out entirely in open loop, the attitude control systems of the aircraft being deactivated. The input orders during each trial are dispatched directly to the airfoils in an automatic manner, independently of the movements of the aircraft. These airfoil orders are all defined in gated form and make it possible to excite the aircraft.
It will be noted that a trials protocol specifies the airfoils which will be called upon in flight during the trials, the deflection level to which these airfoils will be subjected, the duration of deflection, as well as the flight point at which the trials will be carried out.
However, with such a standard trials protocol, and although the controls applied are different at each trial, the output curves all exhibit similar dynamics. A more thorough analysis makes it possible to demonstrate that the response of the aircraft complies with a dominant mode which prevents it being possible to distinguish the other phenomena from the flight mechanics of the aircraft. This dominant mode occurs on all the outputs. Thus, all the aerodynamic effects are correlated. This dominant mode hampers the observability of all the effects. More precisely, this dominant mode corresponds to a combination of aerodynamic effects and prevents the possibility of being able to accurately separate the various effects and of being able to characterize them individually. Consequently, the input calls to the aircraft, during such a standard trials protocol, are poor for identifying all the aerodynamic phenomena of the aircraft.